Dentitheca dendritica ( Nutting, 1900 )

Calder, Dale R., 2013, Some shallow-water hydroids (Cnidaria: Hydrozoa) from the central east coast of Florida, USA, Zootaxa 3648 (1), pp. 1-72 : 35

Dentitheca dendritica ( Nutting, 1900)

Fig. 10a

Plumularia dendritica Nutting, 1900: 67 , pl. 8, figs. 4–6.— Jones, 2002: 217.

Dentitheca dendritica .— Humann, 1992: 73, middle photograph.— Humann & DeLoach, 2002: 73, middle photograph.— Cairns et al., 2002: 55.

Type locality. Bahamas: near Little Cat Island ( Nutting 1900: 67) .

Voucher material. Palm Beach, 1.42 miles (2.3 km) offshore, 30.5 m, 23.vii.1974, Johnson-Sea-Link, JSL1174, diver lockout, one colony fragment, 7 cm high, without gonophores, coll. J. Prentice, ROMIZ B1127.— Palm Beach Inlet, 80 feet (24 m), February 1991, sandy flat, two colony fragments, up to 13 cm high, without gonophores, coll. P. Humann, ROMIZ B1130.

Remarks. Dentitheca dendritica Nutting, 1900 is, as its specific name implies, tree-like in colony form. Hydroids are robust, arborescent, and reach nearly a half-metre high ( Nutting 1900), and as noted two paragraphs below it may grow even taller. According to Humann (1992) and Humann & DeLoach (2002), it is found on reef tops, outcroppings along walls, and flat substrates, particularly in areas swept by currents. The plane of the colony is oriented perpendicular to the direction of water flow.

Sphaerocystis heteronema Fraser, 1943 , originally described from the Bahamas, is considered identical with Dentitheca dendritica ( Calder 1997: 8; Galea 2010: 28). The tropical Indo-Pacific D. habereri ( Stechow, 1909) has generally been maintained as a distinct species (e.g., Ryland & Gibbons 1991; Hirohito 1995; Schuchert 2003; Kirkendale & Calder 2003; Di Camillo et al. 2010). Nutting (1927) found that specimens from the Philippines “agree very exactly” with descriptions, illustrations, and type material of D. dendritica , and he identified them as such. However, Galea et al. (2012) established that gonothecae of D. dendritica originate as replacements of nematothecae adjacent to hydrothecae or on the apophyses, whereas those of D. habereri arise in axils of internode apophyses. Dentitheca bidentata ( Jäderholm, 1920) from Brazil is a much smaller species than D. dendritica , with colonies reaching only about 4 cm high ( Migotto & Marques 1999). Cusps on the hydrothecal margin of that species are both more pronounced and more distant from the hydrocladial axis than in D. dendritica , and hydrothecae are not as deep.

Zoanthids are commonly associated with these large hydroids. Two species were reported by Swain (2009) on Dentitheca dendritica in the western Atlantic, Hydrozoanthus tunicans ( Duerden, 1900) and the newly described H. antumbrosus ( Swain, 2009) , while both Hydrozoanthus gracilis ( Lwowsky, 1913) and Parazoanthus sp. (probably Hydrozoanthus sp. ) have been reported on D. habereri in the Indo-west Pacific ( Di Camillo et al. 2010). Noteworthy is Duerden’s (1900) account of Parazoanthus tunicans (now Hydrozoanthus ), found on a species of hydroid from Jamaica that was likely D. dendritica . The hydroid reached “...as much as 100 cm. high.”

Gonothecae of Dentitheca dendritica were unknown until being discovered and illustrated recently by Wedler (2004, in hydroids identified as D. habereri ). Even more recently, Galea et al. (2012) found that gonophores of both sexes are cryptomedusoids retained within the pear-shaped to conical gonothecae. By contrast, gonothecae of D. habereri are described as bell-shaped ( Hirohito 1995; Schuchert 2003; Di Camillo et al. 2010), and the gonophores of D. bidentata are short-lived medusoids ( Migotto & Marques 1999). According to both Wedler and Galea et al., the duration of gonophore production in D. dendritica appears to be very brief.

Colonies of Dentitheca dendritica are reported to sting bare skin ( Humann 1992; Humann & DeLoach 2002).

Reported distribution. Atlantic coast of Florida. Palm Beach ( Humann 1992; Humann & DeLoach 2002, based on material listed above; Cairns et al. 2002).—Biscayne Bay ( Jones 2002, as Plumularia dendritica ).

Western Atlantic. Florida ( Humann 1992) and the Bahamas ( Vervoort 1968, as Plumularia dendritica ) to the Caribbean Sea ( Galea 2010).

Elsewhere. If Dentitheca habereri is conspecific, the species also inhabits the tropical western Pacific and Indian oceans ( Di Camillo et al. 2010).

Figures

FIGURE 10. a, Dentitheca dendritica: part of hydrocladium with two hydrothecae, ROMIZ B1130, scale equals 0.10 mm. b, Nemertesia simplex: apophysis and basal part of hydrocladium, ROMIZ B1121, scale equals 0.20 mm. c, Nemertesia simplex: part of hydrocladium with hydrotheca, ROMIZ B1121, scale equals 0.10 mm. d, Plumularia floridana: part of hydrocaulus with basal parts of two hydrocladia, and three hydrothecae, ROMIZ B1080, scale equals 0.25 mm. e, Plumularia setacea: part of hydrocaulus with basal parts of two hydrocladia, a female gonotheca, and a hydrotheca, ROMIZ B1111, scale equals 0.20 mm. f, Plumularia strictocarpa: part of hydrocaulus with basal parts of two hydrocladia, and three hydrothecae, ROMIZ B3971, scale equals 0.20 mm.